@stephenw10
Just a quick followup that I figured out the issue to this problem.
The problem had to do with a rule cleanup that took place prior to the upgrade. While while the rules that were cleaned up didn't pertain to the VPN traffic directly, it did reveal that the rules specific to this segment's traffic were impacted by two specific issues. 1. The direction of the traffic flow since a floating rule that altered the gateway used existed. and 2. Quick match was not enabled which means the rules pertaining to the traffic were not being applied immediately and were PROBABLY being addressed by a rule downstream.
some additional tcpdumps that showed the return traffic hitting the firewall on the new VLAN segment for the VPN, but NOT hitting one of our SERVER VLANS where the request originated. This pinpointed the issue as being firewall related. I didn't want to just dismiss it as a bug without further troubleshooting, but was running out of ideas initially.
At any rate, all has been fixed and is working again. Thanks so much again for chiming in!